Plastic compositions



Patented Apr. 13, 1943 PLASTIC COMPOSITIONS Corn'ille O. Strother,Buflalo, N. Y., assignor to Carbide and Carbon Chemicals Corporation, acorporation of New York No Drawing. Application November 21, 1939,Serial No. 305,451

Claims.

This invention pertains to novel plastic compositions composed ofthermoplastic artificial resins or cellulose derivatives intimatelymixed with solid heterocyclic keto-ethers of the group consisting ofpyrones and pyronones which act to reduce the fusion temperature of.such substances without causing them to be softened unduly at ordinarytemperatures.

It has been discovered that such compounds, at temperatures above theirmelting points, which do not vary widely from 100 to 110 C., areexcellent solvents for thermoplastic materials. Upon cooling thesolutions thus formed, a hard material results which is non-extensibleand resistant to fracture. The invention.thus provides for thefabrication of solid articles from heat-sensitive plastic bodies attemperatures appreciably below those required to mold objects withoutinternal strains from these materials. In addition, this discoverypermits articles of intricate design to be formed with sharperimpressions from thermoplastic molding materials since the moltensolution fills the crevices of the mold more readily than the plasticalone when softened by heat. Furthermore, the expensive moldingequipment ordinarily needed is not required. I

It is also possible to make solid objects from the thermoplastic resinsby the addition of an amount of a pyrone or a pyronone compoundinsuficlent to form a fluid solution at elevated temperatures, butadequate to result in extremely viscous compositions from which moldedarticles can be fabricated by an extrusion or an injection process. Thismethod has the advantage that the thermoplastic bodies, many of whichare sensitive to thermal decomposition, need not be a heated to hightemperatures for the relatively long periods which are required inpresent processes for injection molding. In addition, the use of smalleramounts of the softening compounds is beneficial in that somewhatstronger articles of greater clarity are produced.

Pyronones, that is, compounds containing the pyronone ring,

may be formed by the dimerization of diketene, or its isomers, analoguesand homologues, as described in the application of A. B. Boese, J r.,Serial No. 83,930, filed June 6, 1936, now Patent 2,229,204. Forexample, dehydracetic acid, (6-methyl-3- acetopyronone) may be readilyformed by the polymerization of two molecules of diketene. Examples ofpyrones, that is, compounds containing the pyrone ring,

0 C/ \I; ,L

include dimethyl pyrone, diethylpyrone, and similar derivatives.

Typical of the thermoplastic artificial bodies which may be used inmaking the new plastic compositions are: (1) the vinyl resins which maybe made by the polymerization of such vinyl compounds as vlnyl formate,vinyl acetate, vinyl propionate, vinyl chloride, styrene, vinyl ethylether, and vinyl methyl ketone; (2) vinyl resins of the polyvinyl acetaltype which may be produced by the condensation of polyvinyl alcohol withaldehydes; (3) the acrylate resins which may be formed by thepolymerization of alkyl esters of acrylic or methacrylic acid; (4)resins of hydrocarbon nature such as may be obtained by thepolymerization of butadiene, isoprene, butylene, and their halogenderivatives; (5) cellulose derivatives, such as nitrocellulose,cellulose acetate, and the like.

An outstanding class of resins to which the invention is applicable isthe vinyl resins which may be made by the conjoint polymerization ofvinyl halides with vinyl esters of lower aliphatic acids. Preferredresins within this group are those which may be formed by the conjointpolymerization of vinyl chloride with vinyl acetate to produce resinousproducts having a combined vinyl chloride The plastic compositions ofthis invention possess utility for other purposes than the preparationof solid articles. For instance, the plastic compositions may be used asadhesives and, for this purpose, the surfaces to be joined may be firstcoated with the hot fluid solution, for example by knife-coating or byroll-coating. The surfaces are then placed in contact under pressure;heating being required if the solution has solidified. Upon cooling,strong bonds between the surfaces result, This procedure is advantageousin that it does not require the use of volatile solvents which formerlywere needed to first apply the thermoplastic medium in solution to thesurfaces, which, after the solvent had evaporated, were joined by ahot-pressing operation. In a similar manner, the molten composition maybe applied as a coating or finishing composition to paper, textilefabrics, leather, and similar materials. In this application, flexiblefilms are obtained by virtue of their thinness rather than by anysignificant plasticizing action by the pyrone or pyronone compound.

In the adaptation of the plastic compositions for adhesives, it ispossible to join surfaces by first covering them with a mechanicalmixture of the thermoplastic substance with the selected pyrone orpyronone compound and subsequently applying heat and pressure to theassembled composite product. This serves the dual purpose of fusing thecomponents of the plastic composition and of joining the surfaces. Themethod described is of particular utility in making laminated productsfrom plywood.

Several examples will now be given to illustrate the several embodimentsof the invention discussed above:

Example I Fifty parts of a resin made by the conjoint polymerization ofvinyl chloride with vinyl acetate and containing about 87% vinylchloride and having an average macromolecular weight of about 10,000were dissolved at 135 C. in 50 parts of dehydracetic acid (melting point108 C.). Viscous solutions of a consistency somewhat greater thanglycerine were obtained from which hard and durable objects couldreadily be cast. Less viscous molten solutions can be obtained byincreasing the temperature, decreasing the concentration of resin, or byemploying resins of lower macromolecular weight. For instance, 50%solutions by weight of a resin of the same chloride content, but havingan'average macromolecular weight of only about 5,000 to 7,000, have aviscosity approximately that of glycerine.

Similar articles were likewise obtained by casting molten solutions ofhighly polymerized polyvinyl acetate in dehydracetic acid.

Example II This example illustrates the embodiment of the invention inwhich the amount of pyronone or pyrone compound used in conjunction withthe thermoplastic material is less than that required to form a fluidsolution therewith. For instance, 82 parts by weight of the conjointpolymer described in the preceding example were combined with 18 partsof dehydracetic acid at a temperature of about 135 C. to form anextremely viscous. semi-solid composition. Solid articles werefabricated from this both by an extrusion process and by blow molding.These objects were clear, hard, and strong; their clarity resulting fromthe fact that the limit of compatibility of the dehydracetic acid withthis particular resin was not exceeded.

Plastic preparations softening at about 60 C., but strong and hard atordinary temperatures, were prepared from the composition describedabove. These are useful for various purposes,

such as for sealing and for filling crevices in wood and plaster, sincethey may be readily softened at workable temperatures.

Example III Adhesive compositions may be prepared by incorporatingdehydracetic acid with polyvinyl acetate. For example, 30 parts of theformer, by weight, and 70 parts of the latter were made into a moltensolution and applied to the surfaces of several materials, such asglass, rubber, cork, and metal foil. The coated surfaces were put incontact under heat and pressure and strong laminations were obtainedwhen the assembly had cooled. Adhesive compositions of this nature maybe marketed as a mechanical mixture of the dehydracetic acid withgranules of the resin since it has been found that this prevents theparticles of polyvinyl acetate, which has a low softening temperature,from cohering to form a solid block during shipment or storage in warmclimates.

Example IV Fifty parts of polystyrene by weight were dissolved in 50parts of molten dehydracetic acid and the composition allowed to hardenin the form of a thin film. This was then applied to flexible cardboard,of the type suitable for cartons, by a hot-pressing operation. Thecoating was free from pin-holes and was very resistant to oi s.

Example V Seventy parts by weight of second viscosity nitrocellulosewere incorporated with 30 parts of dehydracetic acid at a temperature ofabout 120 C. to form a viscous solution. Durable films, softening atabout C., were deposited from this solution. The term thermoplastic asused herein refers to substances which are normally solid and capable ofrepeated softening under heat.

Modifications of the invention other than as described will be readilyapparent to those skilled in the art to which the invention appertains.For instance, stabilizing agents, pigments, dyes, fillers, and otherconventional ingredients may be included in the plastic compositions.All such embodiments are included within the scope of the inventiondefined in the appended claims.

What is claimed is:

1. Normally solid, thermoplastic composition capable of fusing underheat comprising a heatfusible, normally solid, thermoplastic, artificialresinous body intimately mixed with a fusiontemperature-lowering agentof the group consisting of pyrones and pyronones; both said compositionand said resinous body being normally of substantially the samehardness, and said composition fusing at a lower temperature than saidody.

2. Normally solid, thermoplastic composition capable of fusing underheat comprising a heatfusible, normally solid. thermoplastic, artificialresinous body intimately mixed with dehydracetic acid; both saidcomposition and said resinous body being normally of substantially thesame hardness, and said composition fusing at a lower temperature thansaid body.

3. Normally solid, thermoplastic composition capable of fusing underheat comprising a heatfusible, normally solid vinyl resin intimatelymixed with dehydracetic acid; both said composition and said resin beingnormally of substantially the same hardness, and said composition fusingat a lower fusion temperature than said resin.

4. Normally solid, thermoplastic composition capable of fusing underheat comprising a heatfusible, normally solid polyvinyl acetate resinintimately mixed with dehydracetic acid; both said composition and saidresin being normally of substantially the same hardness, and saidcomposition fusing at a lower temperature than said resin.

5. Normally solid, thermoplastic composition capable of fusing underheat comprising a heatfusible, normally solid vinyl resin which is aconjoint polymer of vinyl chloride and vinyl acetate, intimately mixedwith dehydracetic acid, both said composition and said resin beingnormally of substantially the same hardness, and said composition fusingat a lower temperature than said resin.

6. Normally solid, thermoplastic composition capable of fusing underheat comprising a heat- Iusible, normally solid polystyrene resinintimately mixed with dehydracetic acid; both said composition and saidresin being normally of substantially the same hardness, and saidcomposition fusing at a lower temperature than said resin.

'1. Process for making ahard, normally solid, thermoplastic compositionoi relatively low fusion temperature, which comprises, intimately mixingat an elevated temperature a tusiomtemperatunlowering agent with aheat-fusible, normally solid vinyl resin to form anextremely-viscous-tofluid dispersion, and causing said dispersion toharden by cooling it; said fusion-temperaturelowering agent being of thegroup consisting of pyrones and pyronones; both said composition andsaid resin being normally of substantially the same hardness, and saidcomposition fusing at a lower temperature than said resin. v

8. Process for making a hard, normally solid,

thermoplastic composition of relatively low Mon temperature, whichcomprises, intimately mixing at an elevated temperature dehydraceticacid with a heat-fusible, normally solid vinyl resin which is a conjointpolymer of vinyl chloride with vinyl acetate, to form anextremely-viscous-to-.

l0 fluid dispersion, and causing said dispersion to harden by coolingit; both said composition and said resin being normally of substantiallythe same hardness, and said composition fusing at a lower temperaturethan said resin. I

9. Process for making solid articles or predetermined shape whichcomprises forcing into a mold a molten, extremely-viscous-to-fluiddispersion of a heat-fusible, normally solid vinyl resin with aiusion-temperature-lowering agent of the group consisting of pyrones andpyronones, and causing the dispersion to harden by cooling it; both saiddispersion and said resin being normally of substantially the samehardness and said dispersion fusing at a lower temperature than saidresin.

10. Process for making solid articles of predetermined shape whichcomprises forcing into a mold a molten, extremely-viscous-to-fluiddispersion' of dehydracetic acid with a heat-fusible, normally solidvinyl resin which is a con- Joint polymer of vinyl chloride with vinylacetate, and causing the, dispersion to harden by cooling it; both saiddispesion and said resin being normally 01' substantially the samehardness and said dispersion fusing at a lower temperature than saidresin.

CORNEILLE O. STRO'I'HER.

